Tire Replacement Guidelines

When looking up bicycle tire replacement guidelines on various websites, I often see "3 years" or "3,000 km." It can be difficult to tell if your own bicycle's tires need to be replaced.

For example, if you commute or go to school 5 km one way, that's 10 km round trip per day.

If you commute or go to school about 250 days a year, and don't ride on rainy days, you might ride about 150 days a year.

10 km × 150 days = 1,500 km

This means you'll reach 3,000 km in about 2 years.

And here's a little-known fact: the biggest factor in tire degradation isn't wear and tear.

The biggest enemy is "ultraviolet light."

As a mechanical design engineer, I'm well aware that resin and rubber parts on outdoor machinery degrade severely. I constantly struggle with countermeasures, so I know this from experience.

UV light chemically degrades rubber.

It makes it more prone to cracking and wear, causing adverse effects.

You can mitigate degradation by parking your bicycle in a shaded area or using a UV-cut bicycle cover.

Things to check when replacing

It's difficult to determine the exact timing for tire replacement.

Obviously degraded tires are out of the question, but it can be hard to judge borderline cases.

This time, I have an example of a subtle case, which I will share with images.

Upon inspection, I found a crack in the rim area.

There's a crack, and some rust is visible.

By the way, this is the front wheel.

The rear tire didn't seem to have any cracks.

When replacing, it might be necessary to address not just the tire, but also the bead area.

The tire itself has a crack.

It's necessary to determine how deep the crack is.

As you can see in the image, woven wire-like material is visible through the crack.

This is the casing, which forms the shape of the tire.

Normally, the casing becomes visible due to wear, but here, the crack directly exposes the casing.

It's probably best to replace this one.

I've jumped to the conclusion that it's "better to replace," but I'd also like to check the tread of both the front and rear tires.

This is the condition of the rear tire.

Although it's slightly worn, the tread is still visible, so replacement might be put off a bit longer.

Here's the condition of the front tire.

There isn't much tire wear, so it seems fine to continue using it as is.

Comparing the front and rear tires, it seems that for me, the rear tire wears out faster.

■ Choosing Tires

Well, the front tire had a crack on the sidewall, and the rear tire had some wear.

The front tire definitely needs replacement, and the rear tire's condition is tricky to judge.

However, since I'm replacing the front tire, I decided it would be better to replace the rear tire as well.

Now, once you've decided to replace both front and rear tires, first check your tire size.

The tire size is written on the side of the tire.

You can't tell by looking at the bicycle itself.

Looking at the text on the tire's sidewall, it read as follows:

"MAXIMUM RECOMMENDED INFLATION PRESSURE 110 P.S.I 7.7BAR770KPA"

It looks like a spell.

As someone who isn't from an English-speaking country, I couldn't understand any of the information.

The "MAXIMUM RECOMMENDED INFLATION PRESSURE" part likely refers to the "maximum recommended inflation pressure."

Once I figured it out, it wasn't that difficult.

It seemed to be about air pressure, not tire size.

But since I'm at it, let's decipher the next code too.

The next "110 P.S.I 7.7BAR770KPA" actually contains three pieces of information written consecutively.

Written separately, it's like this:

"110 P.S.I," "7.7BAR," and "770KPA" are the three.

"P.S.I" stands for pounds per square inch, written in the imperial system.

By the way, this unit seems to be used only in countries like the United States, Myanmar, and Liberia.

Even so, it comes first, so America is strong.

The next one, "BAR," is the bar unit.

It was a unit used in Japan in the past.

"Millibar" was also used in weather forecasts.

Lately, it's "hectopascal," right?

The relationship between PSI and BAR is "100 PSI = 6.89 BAR."

In other words, 110PSI = 7.58BAR, but rounded to 7.6BAR.

There is some error, but 110PSI = 7.7BAR is written on the tire surface.

And "KPA" stands for kilopascal.

Since "1BAR = 100 kilopascal," 7.7BAR = 770KPA.

Simply put, three units are written there.

It means all of them indicate the same pressure.

And since converting them is a hassle, their converted values are written for each.

Anyway, the tire size was listed in a different location.

It says "25-622" and "700×25C."

"25-622" written before "700×25C" is the ETRTO standard, representing the rim width and bead width.

The latter part, "700×25C," indicates the tire size: diameter 700 mm (70 cm) × width 25 mm (2.5 cm).

When searching for "700×25C" on Amazon, there were 48 products ranging from about 2,500 yen to about 26,000 yen.

Since both need to match, searching for "25-622" and "700×25C" will be accurate.

Next, check the tire type, as there are three different shapes.

By the way, those shapes are "tubular tires," "clincher tires," and "tubeless tires."

You'll choose while considering their functions and your budget.

There are also colored tires, such as white or red, in addition to black, and puncture-resistant tires that don't get flat.

You'll choose what you prefer and what your budget allows.

Do you have a better idea of when to replace your tires and which ones to choose?

Be sure to check your own tires!

External writer: Koichi Okuno

△ICAN AERO 52 Wide Rim Carbon Wheels